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DIPOL Weekly Review - TV and SAT TV, CCTV, WLAN

No. 33/2007 (Oct 1, 2007)

China accepted new standard in digital television - a change of the guard? The dual DMB-TH (Digital Multimedia Broadcast-Terrestrial/Handheld) standard can be the turning point in digital TV. It is vital development of previously drawn up digital terrestrial standards, allowing terrestrial transmissions of digital TV to home and mobile receivers, both in standard and HDTV resolution. Among the existing on the market standards - European DVB-T, American ATSC, Japanese ISDB-T and the Chinese DMB-TH - the latter is the most advanced one. It is based on TDS-OFDM modulation (Time Domain Synchronous - Orthogonal Frequency Division Multiplexing), more advanced solution that OFDM used in DVB-T, not to mention of ATSC - 8VSB. The new method of modulation, similarly to OFDM, allows multi-channel transmission, which is perfect for conveying large data streams, including HDTV. The technological advantage of TDS-OFDM consists in adding to multi-channel transmission time division multiplexing. Aside from using in video/TV transmissions, TDS-OFDM is planned to be utilized in Chinese WiMAX standard, known as BWA (Broadband Wireless Access), and cellular version Beyond 3G/4G - for the next generation of mobiles. Up to now, China has been recognized as the world's manufacturing center. Majority of products and technologies have been licensed by corporations from USA, Japan, and - since a while - Korea. It looks like this time ends up. A new leader emerges, also in the field of digital TV technology.

The poll on the cover of printed catalog Dipol 2008. Which one will be the cover of our printed catalog in 2008? - from well known designer from Krakow Lukasz Kozak, whose works have been enriching our publications for many years, we have obtained five designs. Like every year, we arrange online voting.

Which one is to be the cover of the catalog that we will send you next year?

They have a recipe for war antennas. War swept through the country a short time ago. This can be seen in the pictures below. Beside the tragedies associated with death of many people, a profound impression is made by the devastated buildings - having been bombed, battered, and torched. After military operations had ended, some people came back to their destroyed houses. Reconstruction of buildings is a long process, but life must go on - the inhabitants wanted to watch TV, to have access to the news sometimes saving their lives (attacks and assaults occurred on a daily basis long after the main conflict had ended). So the popular way of ensuring TV reception has been temporary constructions like that one shown in the picture.

The uncertainty of the future is a thought which crosses the minds of most people living in Bosnia and Herzegovina...

Modern SMATV/MATV systems - some tips for designers. Exchange of the main installation equipment in a building requires considerable financial outlays. It is also a challenge for the residents. It is the reason why such exchange should be avoided. The original cabling has to survive the test of time - the cables used should provide maximum number of available services. They have to ensure good parameters not only in FM/TV bands, but also in satellite IF band (950-2400 Mhz), and in back channel (5-60 MHz). It will enable the residents to have access to satellite broadcasts (with IF/IF converters or multiswitches), as well as to the Internet. The diagram of an installation working up to 2.4 GHz is similar to that up to 862 MHz, but one should avoid to use pass-through layout that is not suitable for employing multiswitches. Of course, all passive components of the installation have to work within 0.05-2.4 GHz frequency band. The optimum topology (star network) consists in connecting cables from every outlet to the central point, e.g. the box in the staircase where there is a multi-output tap. This solution allows easy installation of packet filters in the future, as well as is both more fail-safe and easier to service. All staircases are connected with a splitter, or in the case of larger number of subscribers, there are used additional amplifiers that form two-stage installation. It is also recommended to prepare the installation for connecting cable TV that offers a whole spectrum of services these days. There will be needed place for the box for building amplifier that, in the case of providing cable TV, will take over the function of channel amplifiers used in MATV installation. It is worth to consider leading two coaxial cables from the basement to the node(s), which ensures easier and cheaper bundling of services into packages - only two filters are needed for the most popular division into basic and premium packages.

Diagram of cabling of 10-story building which makes it easier to connect cable TV. Two cables coming out of the cable distribution box in the basement ensure easier and cheaper bundling of services into packages.

Satellite outlet with return path - Signal. The outlet R694140 has two inputs: the first one feeds R (FM), TV, and SAT2 outputs, the second - SAT1 output. Both the SAT1 and SAT2 outputs convey sat IF band, but the latter can also transmit e.g. modulated return signal from satellite receiver.

CCTV - problems with long cables. Luminance information needs 3 MHz band, while chrominance components require at least 4.5 MHz. Characteristics of any coax show higher attenuation for higher frequencies, which may affect the image quality in the case of very long cables, especially those of lower quality. For that reason, color cameras working with long cables require coaxial cables having lower attenuation and better screening efficiency. DIPOL can recommend TRISET-113 E1015_500 or TRISET-11 E1025_200. Another way of improving the situation is use of video signal amplifier which will eliminate the problems with fading colors - VCA-1/2000 M1842.

In the case of long cables and fading colors, the video signal amplifier VCA-1/2000 M1842 ensures improvement of the situation.

CCTV installer's monitor. Adjustments of the camera and lens may be a difficult job, especially when the camera is situated in a place that is hard to reach. In such conditions there is indispensable service LCD monitor MIG-29 M3104. Due to small size (3.5"), the installer can connect it quickly and conveniently to the camera, even standing on a high ladder. The monitor can be powered from the camera's circuit, or from set of eight AA alkaline batteries that can power the configured camera directly from the monitor.

Quality of digital video recorders - speed and resolution of recording. These two parameters are the basic features of any DVR that are given by the manufacturer.Usually the number of frames per second (fps) comprises all inputs, e.g. in the case of 16-ch DVR and 400 fps it means capability of recording 25 fps from every camera.But the real potential of any DVR is characterized by the combination of the both parameters. There is a big difference between a 400 fps/CIF DVR and that 400 fps/ D1. If the manufacturer does not give the both parameters, it is usually an attempt to hide low capability of the equipment.Resolution of images in digital technology is described by number of pixels in horizontal and vertical lines. The popular picture format is CIF (Common Intermediate Format). The picture is formed from macroblocks (16 x 16 pixels), the units that are also used in MPEG processing. Sometimes resolution capability is described by rarer SIF name (Source Input Format) - 352 x 288 pixels in PAL system. Modern DVRs can use Full D1 resolution (PAL - 720 x 576 pixels) and Half D1 - 720 x 288. CIF formats:

4CIF - 704 x 576,

CIF - 352 x 288,

QCIF - 176 x 144,

The line is continued in HDTV:

"720p" - 1280 x 720,

HD 1080 - 1920 x 1080.

For comparison, we list the resolutions of displays used in digital devices, computers etc, that have also been adopted by some manufacturers of IP cameras:

QQVGA - 160x 120,

QVGA - 320 x 240,

VGA - 640 x 480,

SVGA - 800 x 600,

XGA - 1024 x 768,

SXGA - 1280 x 1024,

UXGA - 1600 x 1200,

QXGA - 2048 x 1536.

Resolution of images in CIF and VGA standards

AI lens - how is it built and how does it work? - Part 4. How does work Video Iris control? Video Iris control is implemented inside the lens, not the camera. There are used only three cables: 12 VDC supplying voltage, common, and Video signal from the camera. The amplifiers and "Level" pot (and sometimes "ALC" pot for setting reaction speed) are put inside the lens housing. It means the control system is shifted from the camera to the lens (compare with the previous part). So the Video Iris camera is generally less complicated than its DC Iris equivalent (just opposite the lenses). In this situation most of DC Iris cameras also have possibility of controlling Video Iris lenses, with a switch changing functions of the control cables.

Block diagram of the camera circuitry controlling Video Iris lens.

Security in VVD networks. Digital networks where we send images (Video), sound (Voice) and other digital information (Data) are called VVD - Video-Voice-Data. Remote monitoring, aside from self-evident advantages, carries a risk for local network, as requires access to IP cameras through the Internet. Typical solution that partially protects the system is redirection of ports to IP cameras placed in the local network. However, it still enables the potential intruder to get relatively easy access to that network.

IP cameras placed in local network

Another, safer solution is based on the idea of locating IP cameras in the local network, but between two routers. The first one gives access to the cameras from the Internet, the second separates the traffic between local network and the protected sub-network with users' computers and e.g. file server. With this solution, IP cameras are seen from the side of the computers in protected sub-network as any remote computer. The issues connected with structure and configuration of such result network are quite complicated and definitely require actions that should be taken by IT specialist in the field of network security.

IP cameras placed in local network, the computers located in protected sub-network

A half meter higher and it works - the Fresnel zone. The picture below has been taken from the place in which one of the antennas of 2.4 GHz wireless link is mounted. The second device can be seen as a white spot. The distance is about 300 m, with mutual visibility. In the beginning, the antennas were placed 2.2 m above the roof and 1.4 m above chimneys. About 30 m from the distant antenna, on the left, there is a tree, this one above the line of chimneys. The edge of its crown is around 1.5 - 2 m from the antenna-antenna axis. The growth of the tree during the summer was the reason the link failed to work. The antennas had to be raised by 50 cm to restore the link.

Fresnel zone is one of the most important concepts connected with propagation of electromagnetic waves which is indispensable to assess parameters of wireless link. It is the area actively participating in transmission of radio signal energy. Shape of this area is an ellipse in longitudinal section, and circle in cross-section. Radius of this circle is a function of the ratio of distances between antennas - it has the maximum value in the middle of the link. The importance of first Fresnel zone comes from the fact that almost all energy of the signal is conveyed via this space.

The shape of Fresnel zone

An example of incorrect installation. The installer haven't secured mutual visibility of antennas. The radio link does not work properly.

An example of correct link. Visibility of antennas and no barriers in the first Fresnel zone.

Engagingly about Antennas - VI Summer 2007 Dipol Competition is closed. We have just closed the door on incoming works. The fruit of this edition will be adjudicated by juryman Pawel Zechenter - highly regarded photographer from Krakow. We invite you to examine the pictures, also to form your own opinion - will it be concurrent with the result of the Contest? The winners will be announced in the next issue of the Review.

Exhibitions and trade fairs. We invite those who cannot arrive in Poland at SatKrak in Krakow (18-20 Oct 2007) and Alarm in Kielce (8-10 Nov 2007) to visit our virtual stands.

Dipol at SatKrak

DIPOL at Alarm

DIPOL has new logo. After 17 years we change our logo. The official presentation of the logo will take place during SatKrak and Alarm events. But you can visit our virtual stand and view it now. We hope the sign will accompany us at least for the next 17 years!

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